ola_set_priority: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/ola_set_priority - from package: ola

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ola_set_priority - from package: ola

You may install the required package with command apt-get install {package}

Error in other languages:
ola_set_priority: bevel nie gevind nie
ola_set_priority: comandă negăsită
ola_set_priority: comando não encontrado
ola_set_priority: commande introuvable
ola_set_priority: command not found
ola_set_priority: käsku ei ole
ola_set_priority: không tìm thấy lệnh
ola_set_priority: komanda nerasta
ola_set_priority: Kommando nicht gefunden.
ola_set_priority: kommandot finns inte
ola_set_priority: komut yok
ola_set_priority: nie znaleziono polecenia
ola_set_priority: níor aimsíodh an t-ordú
ola_set_priority: no se encontró la orden
ola_set_priority: no s'ha trobat l'ordre
ola_set_priority: opdracht niet gevonden
ola_set_priority: parancs nem található
ola_set_priority: perintah tidak ditemukan
ola_set_priority: príkaz nenájdený
ola_set_priority: příkaz nenalezen
ola_set_priority: команда не найдена
ola_set_priority: командата не е открита
ola_set_priority: 命令找不到
ola_set_priority: コマンドが見つかりません